FIG. 14 is a sectional view of conventional plasmon sensor 100 adapted for detecting viruses, for example. Plasmon sensor 100 includes prism 101, metal layer 102 having a smooth surface situated on a lower surface of prism 101, insulation layer 103 having a predetermined dielectric constant and having a smooth surface situated on a lower surface of metal layer 102, and acceptors 104 fixed to a lower surface of insulation layer 103.
A surface plasmon wave that is a compression wave of electrons exists at the interface between metal layer 102 and insulation layer 103. Light source 105 located above prism 101 applies p-polarized light to prism 101 under a condition of total reflection. At this moment, an evanescent wave is generated on surfaces of metal layer 102 and insulation layer 103. The light totally reflected on the surface of metal layer 102 enters into detector 106 that detects an intensity of the light.
Here, energy of the light supplied from light source 105 is used to excite the surface plasmon wave when a matching condition of wave numbers under which the wave number of the evanescent wave is consistent with the wave number of the surface plasmon wave is fulfilled, thereby decreasing the intensity of the reflected light. The matching condition of wave numbers is dependent upon an incidence angle of the light irradiated from light source 105. Therefore, the intensity of the reflected light decreases at a certain incidence angle when measured with detector 106 while changing the incidence angle.
A resonance angle at which the intensity of the reflected light becomes the minimum depends on a dielectric constant of insulation layer 103. The dielectric constant of insulation layer 103 changes when an analyte which is an object substance in a test sample is bound specifically with acceptors 104 and form a product of specific binding on the lower surface of insulation layer 103, which in turn changes the resonance angle. This allows a binding strength, speed and the like of the specific binding reaction between the analyte and acceptors 104 to be detected by monitoring the change in the resonance angle.
Plasmon sensor 100 includes light source 105 for supplying the p-polarized light and prism 101 disposed on metal layer 102, thus having a large size and a complex structure.
Patent Literature 1 discloses a conventional plasmon sensor similar to plasmon sensor 100.